In the prior art, demand control, where energy consumption is suppressed for a certain period of time, is performed with regard to a heat source system having a plurality of heat source units. A device which is shown in, for example, Japanese Unexamined Patent Application Publication No. 2007-212038 is known as an example of a demand control device which performs demand control. The heat source system in Patent Literature 1 includes a heat source unit where it is possible to control energy consumption and a heat source unit where it is not possible to control energy consumption. The plurality of the heat source units where it is possible to control energy consumption have the same capacities and load characteristics. The demand control device according to Patent Literature 1 uses a method where energy consumption is suppressed simultaneously by all of the heat source units where it is possible to control energy consumption at a given proportion so as to achieve the requested energy consumption.